Because of births, deaths, good news, bad news, good movies, bad movies... Here's the scoop on what gets our tears flowing

The editor who asked me to write this story did so because he knows I'm a crier. He's seen me cry at appropriate times (on 9/11), at inappropriate times (in editorial meetings), and at just plain weird times (when my pen runs out of ink). Like most men, he's scared when I cry. I can see it in his eyes as he edges back from my desk: What's the matter with her? Is she coming unhinged? How can she get so upset over a lousy pen?

Tom, you moron, it's got nothing to do with the pen. Any woman could tell you that.

But what it does have to do with is something I never really gave any thought to. I cry because, well, because. Because I feel bad. Because it feels good. Because I have unresolved attachment issues and am regressing to a preverbal state to reforge a symbolic internal connection to my mother.

Or maybe it's because I'm getting my freaking period, okay?

Cry, Baby

I first cried on the day I was born. Like most babies, I cried at a pitch between C and C-sharp. Yet my mom could pick me out by the sound. I cried because it was all I could do, the only tool I had to summon food and comfort. I cried more and more for the first 6 weeks of my life, then at a steady rate — mostly in the evening — until I was 12 weeks old, when I began to cry less. That was also when I started to cry tears you could see.

Tears — made up of mucus, water, and oil — had already been moving across my eyes every time I blinked. These constant, involuntarily produced "basal tears" — from 5 to 10 ounces a day — drain through small holes in the corners of the eyelids into the nasal cavity, which is why your nose runs when you cry.

Just at the point when I was beginning to smile and make eye contact and coo responsively, though, I was also learning to use my crying more cleverly, experimenting with pitch and duration and tone. And my tears overwhelmed my body's drainage system, spilling over my eyelids. Puling gets old. But who can resist a baby's tears?

Not even a baby, it seems. Whenever my mother set me beside a crying playmate, I would start up. Mom laughed, but NYU psychology professor emeritus Martin Hoffman, Ph.D., thinks I was demonstrating that empathy is one of the first emotions humans experience. Babies don't usually cry when they hear recordings of their own crying — but do when they hear that of others.

64 Cries per Year

Randy Cornelius, Ph.D., a psychology professor at Vassar College, is one of only a few dozen scientists in the world who study tears. The dearth of researchers may be due to the thorniness of even the simplest questions about crying. For instance: Why do women cry more than men?

"We're not sure," says Dr. Cornelius, who despite his sorrowful specialty is quite cheery. "There's been speculation it has to do with the way male and female brains are put together. But that hasn't panned out yet." He points out that up until children start school, boys and girls cry at equal rates, which suggests a societal root: Parents let girls sniffle but crack down on crybaby boys as they grow. The discrepancy could be an evolutionary adaptation, though. Crying, Dr. Cornelius says, is how we signal to other humans that we're vulnerable and in need. Women are good at vulnerability; we share our emotions as a sign of trust, and that trust helps us survive. But a male Survivor contestant who bursts into tears might as well tattoo "Vote Me Off" on his chest.

One substance being studied in connection with crying is the hormone prolactin, levels of which increase in women during puberty, menstruation, pregnancy, and breastfeeding, as well as when we're under stress. We average up to 60 percent more prolactin in our bodies than men. William Frey, Ph.D., biochemist and author of Crying: The Mystery of Tears, theorizes that prolactin lowers women's emotional bar by stimulating the endocrine system, which makes us more prone to tears.

And we do cry more — on average, 64 times a year, compared with 17 times for men. We cry when we're sad or frustrated or angry, whereas men cry at major losses, like death; when they get frustrated, they just get mad. Ask a man the last time he cried in front of someone else and chances are he'll have a hard time remembering. A woman won't.

But a funny thing happens as we reach midlife. Women cry less and get angry more — just as our levels of female hormones drop off, leaving a higher concentration of the male hormone testosterone. In men, a decline in testosterone makes for increased impact from their female hormones. And guess what? As guys get older, they get angry less — and cry more.

Two Sources for Tears

As physical creatures, we're accustomed to straightforward cause and effect: You scrape your knee and you bleed. So we're mystified by the link between our physical nature and our emotions. How do we get from hurt feelings to tears?

Crying, explains Darlene Dartt, Ph.D., a cellular physiologist at Harvard's Schepens Eye Research Institute, started out as a protective response mechanism. There are sensory nerves in the cornea, just like the pain nerves in your skin. When you walk into a strong wind or slice into an onion, the nerves in the eye send impulses to the brain stem, which regulates involuntary processes like heartbeat, swallowing, and breathing. The brain stem releases hormones that travel to the glands along the eyelids and tell them to produce tears, which wash away the irritant. These are "reflex tears."

But the nerves in the cornea also reach higher in the brain, into the cerebrum, and that's where "emotional tears" — the kind you shed watching Titanic — get their start. When Jack Dawson dies, you feel sad. Your sorrow is registered in the cerebrum, which signals the endocrine system to release hormones that travel to the eyelid glands and generate tears. It's no coincidence, it seems, that the cerebrum is also the part of the brain that controls speech. Crying is a form of communication, likely the earliest form, and certainly the one we use first.

Why do we cry when we're sad rather than when we're, say, curious? One of the first crying researchers, Paul D. MacLean, M.D., Ph.D., an NIH neuroscientist emeritus, linked it to an ancient ritual; he speculated that as early humans cremated dead loved ones, the reflex tears produced by the smoky pyres combined with the emotional devastation our ancestors felt. The result was an inexorable connection between death and tears, sadness and sobbing.

A Teary Time of the Month?

I try to control my crying. But once a month, I lose the battle. Two days before my period begins, I fall into a bottomless emotional pit in which I sob for, well, no good reason at all. You know what I'm talking about.

Which is why you won't be any happier than I am with Ad Vingerhoets, Ph.D., a psychology professor at the Tilburg University in the Netherlands. Dr. Vingerhoets's studies show that while in Western cultures women link crying to their menstrual cycles, in non-Western cultures, they don't. What's more, when we keep diaries of when we cry, there's no correlation whatsoever between weeping and menstruation, regardless of where we live.

Heresy!

It could be that we connect crying to menstruation because we like to think of tears as part of our deeper, uncontrollable animal nature; that gives us permission to indulge in those cry-till-you-gag jags. Yet how can tears be animalistic when we're the only animals that cry? It's more likely that we weep because we're so highly evolved — because our minds tease out endless ribbons of regret and conjecture and what if. Tears, says Tom Lutz, author of Crying: The Natural and Cultural History of Tears, distract us from all that inner anxiety by sending us off to find a Kleenex and blow our noses. They relieve our turmoil by refocusing our attention from the mental to the physical.

In that sense, tears are about buying time until we heal. An English scientist who set out to determine what sort of music makes us cry found we tear up when a grace note delays the return to the tonic — the base note in a scale. We know what we expect from a melody. When our expectations are thwarted, we weep. If there's any constant to crying, it may be that our bodies and minds seek a return to balance, an equilibrium. When a baby sobs for its mother, or a teenager weeps at a friend's betrayal, or a woman mourns her dead husband, the common thread is a longing for happiness once had but lost. Tears are our response to life's unfairness. We cry to try to make things right.